A panel-mountable header connector includes conductors and a housing. The housing holds the conductors in a cavity of the housing. The housing has a front end and a rear end. The housing has a latch set and a stop feature which define a panel mounting zone therebetween. The panel mounting zone is configured to align with an opening in a panel when the housing is mounted to the panel. The latch set is configured to engage a front side of the panel, and the stop feature is configured to engage a rear side of the panel to retain the panel in the panel mounting zone. At least one of the latch set or the stop feature is stepped such that a width of the panel mounting zone is variable to accommodate the panel having one of multiple thicknesses.